The long term objective of this project is to elucidate the mechanisms by which gibberellins affect plant growth and development. The effects of this plant hormone on growth and development are seen in the flowers of tomato plants that are deficient in gibberellin. The flowers produced on these plants are dwarfed and infertile because they are blocked at an intermediate stage of development. Exogenous application of gibberellin restores normal and fertility. The specific aims of this project are to identify plant genes whose expression in flowers is regulated by gibberellin, and to begin to elucidate the mechanism of this regulation using both molecular and genetic techniques. Using a molecular approach, we will clone genes whose expression in flowers of gibberellin-deficient mutants is directly affected by the application of gibberellin. These genes will be characterized by determining their spatial and temporal expression patterns followng gibberellin-treatment of gibberellin-deficient flowers. The DNA sequence of each gene will be determined and experiments will be initiated to identify DNA sequence elements that may play a role in gibberellin-regulated gene expression. Using a genetic approach, we will generate a number of temperature-sensitive, gibberellin-insensitive mutants that are affected in flower development. The expression of gibberellin- regulated genes will be studies in these mutants using temperature-shift experiments. The data from these experiments will allow us to construct models of the mechanism by which gibberellins influence gene expression. These data will provide basic information that will enable us to study cis- and transacting factors involved in gibberelllin-regulated gene expression.